Pneumatic cushioning device.



I. GOWLES & E. H. MAODOWELL.

PNEUMATIC OUSHIONING DEVICE. APPLIOATIONPILED 001'. 2a, 1909.

Patented Sept. 12,1911.

3 SHEETS-SHEET 1.

I. COWLBS & E. H. MACDOWELL.

PNEUMATIC CUSHIONING DEVICE. APPLICATION FILED OUT. 23, 1909.

Patented Sept 12, 1911.

.3 SHEETS-SHEET 2.

PNEUMATIC GUSHIONING DEVICE.

APPLICATION FILED OCT. 23, 1909. 1,002,822, Patented Sept. 12, 1911.

3 SHEETSBHEET 3.

UNITED STATES PA ENT OFFICE.

IRVING COWLES AND ERNEST H. MACDOWELL, OF CHICAGO, ILLINOIS.

PNEUMATIC CUSHIONING DEVICE.

Specification of Letters Patent. Patented Sept. 12, 1911.

Application filed'Qctober 23, 1909. Serial No. 524,283.

T all whom it may concern: Be it known that we, IRVING COWLES and ERNEST I-I. MAcDownLL, citizens. of the United States, residing at Chicago, in the county of Cook and State of'Illinois, have invented certain new and useful Improvements in Pneumatic Cushioning Devices;

- and we do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains'to make and use the same. i

This'invention relates to a novel construction in cushioning means for interposition between two relatively movable bodies, the object beingto-pgovide' simple, and efficient means for the prevention of transmission of sudden jar from one bodyto the-o her, and to provide a. simple method for determining the degree ofcushioning efiect produced, and consists in the features of construction and combinations of parts of the apparatus and in the several steps of the method hereinafter fully claimed.

In the accompanying drawings illustrat-' ing a suitable embodiment of apparatus for carrying out our invention: Figure '1 is a plan view of the running gear and bodysupporting. frame of a vehicle equipped with cushioning means constructed in accordance with our invention, the vehicle described and body beingomitted from illustration. Fig. .-2 is a central vertical section of the same on the line 2-2 of Fig. 1. Fig, 3- is a central vertical section of one of the cylindersemploy'ed. 'Fig. -4. is a detail sectional view' of a check-valve employed. Fig. 5 is a fragmentary detail side elevation of another embodiment of our:

apparatus.

to and has for its essential object the provision of means whereby the resiliency of the cushion may be changed and varied to suit the requirements of the vehicle to which it is applied and to this end we make use of well-known physical laws. I

' Pleasure or passenger vehicles are equipped usually with springs which are relatively soft and very resilient it being generally true of this class of vehicles that the weight of the vehicle body greatly exceeds the maximum load, while in freight carrying vehicles the maximum load greatly exceeds the weight -of the vehicle body.

Consequentlyin the pleasure vehicle the difference between minimum and maximum loads on the springs or cushions is relatively small in proportion to the minimum load While in the freight carrierit is relatively very great. In the one case the comfort and eas'eof the passengers is the main consideration while in the other it is only the safety of the merchandise being transported.

Therefore the springs or cushions of such vehicles areintended mainly to prevent transmission of destructive jars either to the merchandise or to the running gear. i

The degree of the cushioning efiec't obtained is dependent entirely upon the distance the load moves from its normal position by the jar to the pointat which such jar is neutralized by the resistance of the cushion. Where the strokeis long and the resistance gradually increased, the jar is felt to a less degree than where the stroke is relatively short and the'increase in re- 'sistanceis correspondingly sudden.

The regulation of the. rapidity of increase of resistance in the cushion constitutes the essence of this invention and its accomplishment in a simple andefiicient manner its essential object.

In carrying out our present invention we employ substantially the same devices as are shown and described in our companion application above mentioned together with such additional apparatus as is necessary to enable us to successfully attain the object above stated. 7

The running gear of the vehicle consists of wheels 1, axles 2- and the side bars -3 to which the axles are secured, the said side bars being equipped at their ends with vertical projections *4?- constituting guide rails between which the side bars -5- of the j vehicle body are vertically .movable-,

relative longitudinal movement between the -body and-the running gear. The -said side bars '3 and axles 2Q constitute the running gear-frame while the bars 5 support the Vehicle body and we will therefore hereinafter refer to these parts as the running gear frame these parts of-a vehicle suited to ourpursuited to our needs.

Supported on-thelbodyframe is a tank orreservoir 6 for fluid under pressure,

it beingessential to the carrying out of our invention that said tank or reservoir be made of metal or other, suitable] inflexible material and of sufiicient strength to resist a relatively very high pressure. The said tank 6 is .connected with the delivery end of an air compressor 7- operable either by hand or power, and with a tank or reservoir 8- fora suitable liquid such as oil, the last-named connection including a pump 9 for transferring liquid from the reservoir 8 to the tank '6 and a valve-controlled pipe 10-'-for discharg ing liquid from the tank '-6 to the res- ,ervoir .8, the pump '9 being either hand or power actuated. The airpump connection includes a blow-01f controlled by the valve l1 for relieving the pres sure in the tank 6.

'Interposed between the running gear .frame and the body frame is a plurality frames is not material to the of cylinders -l2 which. preferably are supported on the running gear frame and in which pistons .--13 are reciprocally movable, the piston-rods 14?- being secured to the body. frame. The particular points of connection and the specific manner of effecting such connections of cylinders and piston rods with the respective present. invention except that the% shall be suitable to meet requirements. ach .of the cylinders 'l2 is connected at one end with the tank -6-I by means of a pipe'-l5' in which a check-Valve 16-. is interposed which will'pern'iit flow of fluid from the cylinder to the tank butwill prevent its flow in the opposite direction. A. by-pass duct.-'17- is provided aroundeach checkvalve and is controlled by a suitable hand operated valve l8- by which it -may be partly choked to retard flow from the tank 6 to the cylinder to the requisite extent required for the proper carrying out of the invention. The cylinders 12' with the pistons '-13- represent a suitable embodimentof fluid pressure chambers of varying capacity having inflexible walls which are necessary. to the proper carrying out of the said projections preventing i and body frame respectively. The construction shown is intended only to illustrate embodiments ofarrangement -vious. tank -6- at or adjacent the lowest point ber of the cylinder also constitutes a fluidpressure chamber which performs a function as fully described in our'companion application. The said function does not, how-' ever, affect the present invention and particular description thereof and the means for its accomplishment will. therefore be omitted herefrom. The fluid contained in the pressure chambers of the cylinders supports the vehicle body and contents by means of the'piston 13- as will be 0b.- The pipes 15 connect with the therein and are adapted to conduct only the liquid contents of the said tank -6 and of the cylinders 12 from each to the other.

It is well known that liquids are relatively incompressible, and, therefore, inelastic while gases are extremely elastic and maybe compressed to a very great extent to reduce the volume of space occupied therebyz; In our device we take advantage of the elasticity of air to provide a resilient cushion and employ liquid as the vehicle for transmission of the air pressure in the tank 6 to the different cylinders and pistons therein to support the load. The air in thetank, therefore, actually supports the vehicle body, and such, air' must necessarily be under the requisite pressureto sustain such load. The volume of space occupied by the air cushion in proportion to the cross-sectional area of the pressure chambers of the cylinders, will, independently of the air pressure, determine the resiliency or elasticity of the cushion. .That is to say. an

air cushion under pressure of 100 lbs. to thesq. in. occupying a cubic foot of space will be more resilient and elastic than an air cushion under the same pressure but occupying only one-half the volume of space for the reason that each cu. in. of contraction'of space occupied will increasethe air pressure under the'lasbnamed condition to a greaterextent than in the first-named and consequently the pressure under the lastnamed condition would be increased to the point necessary to neutralize the momentary increase in load due to a jar by a less displacement of liquid from the cylinders than would be necessary .under the first-named condition to effect this result.' In other words the supporting power of the cushions would be the same in both instances but the power of resisting impact would be greater where the volume of -air is less.

Thus if the piston area in each cylinder is twenty-five square lnches, or a total of one hundred square inches in the four and the.

air pressure in the tank *6- is one hundred lbs. to the square inch, the supporting power of the cushion would be ten thousand lbs. regardless of the volume of space 00-' 7 sure would result, but if the volume of space occupied is only 500 cuin. then the-contraction resulting from the aforesaid movement of all pistons would be twenty per cent. and.

the increase in pressure correspondingly greater. Therefore, the increase in resistance to displacement of the liquid in the cylinders would be more rapid under the last-named condition than under the firstnamed. v I

To attain the best results the supporting power of the spring or cushion must not greatly exceed the load else the primary resistance of the spring 'or cushion would defeat its object by too great rigidity of the support afforded thereby. On the other Hand too great elasticity of the spring or cushion or too little would result either in the accumulation of resistance too slowly or too rapidly thereby either rendering possible the complete displacement of all liquid in the cylinders and the pounding of the pis- ..tons on the cylinder heads or causing a jerkystop. Therefore the cushion should be primarily adjusted to substantially balance the load and the stiffness of the cushion regulated to. a degree to insure the accumu-' lation of the maximum resistance requisite to neutralize the heaviest jar likely to be encountered before the pistons can approach dangerously near the downward. limits of their movement.

The first condition is easily regulated by adjusting the air pressure which may be effecte'd' either by operating the compressor -7- to effect an increase, or operating the blow-oft -11 to efi'ect decrease. The -vol ume of space occupied by the air cushionis. regulated either by operating the pump 9 to'deliver into the tank -6 or by operating the valve in pipe 10- to permit escape of some of that contained in the said tank. Either of the last-named operations would necessarily cause variation in the air pressure and inleifecting adjustment it is preferable to first adjust the volume of space to be occupied by the air cushion and to subsequently adjust the pressure.

Any suitable means'for reading the level of liquid in the tank -6-- may be provided and likewise a pressure gage for reading the air ressure. w

T e small by-pass ducts around the checkvalves prevent the return of displaced liquid to the cylinders as rapidly as it leaves them and thus cause a slow' and gradual reaction and elevation after sudden depression.

In heavy trucks the rear wheels usually carry a greater load than the front and in adapting our invention to this class of vehicles the cylinders supporting the greater load may .be of greater diameter or the stroke of the piston may be increased or both so as to proportion the'cushioning effect to the load upon different partsof the vehicle.

While we have shown and described all cylinders as being connected with a single tank -6- it will be apparent that this par ticular arrangement is capable of variation to suit widely different requirements, the

appartus being intended to be varied to suit its adaptation to all purposes. Thus as shown in Fig. -5 two of said tanks 6- may be provided, one tlrereof being connected with the cylinders supporting the rear end portion of the body and the other with those supporting the forward end portion.

Each of said tanks may .be separately connected with the source of supply of air as by the pipe -19- and the valve controlled branches -20 and -21-. Said tanks 6' are also separately connected with the reservoir -8 by means of the pipe --22- and its valve-controlled branches -23 and 'Q4E and similarly connected in the other direction by means of the pipe '25 in which the pump '9 is interposed, the lastnamed connections being controlled by means of the valves 26 and -27-. This arrangement may be further modified tomeet certain conditions but it is preferable to emplo as few valves as possible and maintain the apparatus as simple as is consistent with its adaptation to' any given purpose. J

'We claim as our invention:

. l. In-a pneumatic spring device, the combination with fluid pressure cushioning devices interposed. between two relatively movable members, and a reservoir connected with said devices, an air space in said reservoir containing air under ressure, a liquid in'said re'servoirpartly filling the latter and constituting the vehicle for communicating the pressure in said reservoir to said fluid pressure dushioning devices,of a tank contaming a liquid supply, and means communicating with said tank and reservoir. for supplying liquid from the tank to the reservoir and for exhausting liquid from the latter 7 into the tank thereby increasing and decreasing the volume of liquid within the res-..

ervdir to vary the resiliency of the cushion.

2. In a pneumatic spring device, the combination with fluid pressure cushioningdevices interposed between two relatively movable members, and a reservolr connected with said de'vices,'-Ian air space in said reservoir containing air under pressure, and a-: liquid in the other thereof to resgectively increase and said reservoir partly filling the latter and condecrease the volum stituting the vehicle for communicating the named reservoir. pressure in" said reservoir to said fluid pres- In testimony whereof we have signed our 15 sure cushioning devices, of a compressor and names in presence of two subscribmg witliqu-id in said firstvan exhaust 'valve'connected withsaid reser4 nes'ses.-,

' voir tojvary the volume and pressure of air IRVING COWLES, therein,-a second reservoir for liquid, con- ERNEST H. MACDOWELL. nections betweenthe same and said first- Witnesses! named reservoir, 2, pump mterposed in one Rnnom n WMQLo'rz; of said eonneetlons and a valve interposed in M. M. Bom. 

